Description:Large hemispherical boulders on the reef, up to 180 cm in diameter. Similar to Siderastrea radians , but the cups are shallower and larger. Cups to 5 mm across, with 50-60 septa per cup (S. siderea corallite).

Color:Light brown.

Habitat:Generally present above 40 m, common at about 10 m. At sheltered locations.